Fixing device detecting abnormalities at a temperature lower than fixing temperature and image forming apparatus

Abstract

A fixing device includes a fixing unit including a pressing device and a heating device and that fixes an image formed on a recording medium by nipping the recording medium with the pressing device and the heating device; a driving device that drives the fixing unit; a load detector that detects a load applied to the driving device; and an abnormality detector that detects abnormality in the fixing unit with reference to the load generated when the recording medium passes through the fixing unit.

What is claimed is: 
     
       1. A fixing device comprising:
 a fixing unit including a pressing device and a heating device, the fixing unit configured to fix an image formed on a recording medium by nipping the recording medium with the pressing device and the heating device; 
 a driving device configured to drive the fixing unit; 
 a load detector configured to detect a load applied to the driving device; 
 an abnormality detector configured to abnormality in the fixing unit with reference to the load generated when the recording medium passes through the fixing unit; and 
 a temperature detector configured to detect a temperature of the fixing unit, 
 wherein if the temperature detected by the temperature detector is lower than a fixing temperature at which the image is fixed, the abnormality detector is configured to detect whether or not the fixing unit has any abnormality by allowing the recording medium to pass through the fixing unit. 
 
     
     
       2. The fixing device according to  claim 1 , wherein the abnormality detector detects whether or not the fixing unit has any abnormality with reference to a relationship between the temperature detected by the temperature detector and a change in the load generated when the recording medium passes through the fixing unit. 
     
     
       3. The fixing device according to  claim 1 , wherein if a period of time over which the temperature of the fixing unit becomes lower than a fixing temperature at which the image is fixed has elapsed since a last execution of the fixing by the fixing unit, the abnormality detector detects whether or not the fixing unit has any abnormality by allowing the recording medium to pass through the fixing unit. 
     
     
       4. The fixing device according to  claim 1 , wherein the load generated when the recording medium passes through the fixing unit and with reference to which the abnormality detector detects whether or not the fixing unit has any abnormality is a load generated during at least part of a passing period over which the recording medium passes through the fixing unit, the passing period being a period excluding an entering period over which the recording medium enters the fixing unit and an exiting period over which the recording medium exits the fixing unit. 
     
     
       5. The fixing unit according to  claim 1 , wherein the recording medium is one of a plurality of recording media having different thicknesses, and the abnormality detector detects whether or not the fixing unit has any abnormality by selectively allowing a thickest one of the plurality of recording media to pass through the fixing unit. 
     
     
       6. An image forming apparatus comprising:
 an image forming device configured to form an image on a recording medium; and 
 the fixing device according to  claim 1  configured to fix the image on the recording medium. 
 
     
     
       7. The image forming apparatus according to  claim 6 , wherein the image forming device is configured to form no image on the recording medium when whether or not the fixing unit has any abnormality is detected with reference to the load generated when the recording medium passes through the fixing unit. 
     
     
       8. The image forming apparatus according to  claim 6 , further comprising:
 a transport device configured to transport the recording medium after an image formed on one side of the recording medium is fixed by the fixing device, the transport device transporting the recording medium such that another image is formed on an other side of the recording medium by the image forming device; and 
 a controller configured to control the transport device such that the abnormality detector detects whether or not the fixing unit has any abnormality by allowing the recording medium to pass through the fixing unit before the temperature of the fixing unit reaches the fixing temperature at which the images are each fixed, and such that the images are formed on the recording medium by the image forming device after the temperature of the fixing unit has reached the fixing temperature. 
 
     
     
       9. The image forming apparatus according to  claim 7 , further comprising:
 a transport device configured to transport the recording medium after an image formed on one side of the recording medium is fixed by the fixing device, the transport device transporting the recording medium such that another image is formed on an other side of the recording medium by the image forming device; and 
 a controller configured to control the transport device such that the abnormality detector detects whether or not the fixing unit has any abnormality by allowing the recording medium to pass through the fixing unit before the temperature of the fixing unit reaches the fixing temperature at which the images are each fixed, and such that the images are formed on the recording medium by the image forming device after the temperature of the fixing unit has reached the fixing temperature. 
 
     
     
       10. A fixing device comprising:
 fixing means including pressing means and heating means, the fixing means configured to fix an image formed on a recording medium by nipping the recording medium with the pressing means and the heating means; 
 driving means for driving the fixing means; 
 load detecting means for detecting a load applied to the driving means; 
 abnormality detecting means for detecting abnormality in the fixing means with reference to the load generated when the recording medium passes through the fixing means; and 
 a temperature detecting means configured to detect a temperature of the fixing means, 
 wherein if the temperature detected by the temperature detecting means is lower than a fixing temperature at which the image is fixed, the abnormality detecting means is configured to detect whether or not the fixing has any abnormality by allowing the recording medium to pass through the fixing means.